diff --git a/ChangeLog.md b/ChangeLog.md
--- a/ChangeLog.md
+++ b/ChangeLog.md
@@ -1,5 +1,9 @@
 # Revision history for elm-export-persistent
 
+## 0.2.0 -- 2018-03-12
+
+* Fixed compilation issue with missing ToJSON constraint on Entity keys
+
 ## 0.1.2 -- 2017-02-07
 
 * Fixed bug with missing id field from single field tables
diff --git a/elm-export-persistent.cabal b/elm-export-persistent.cabal
--- a/elm-export-persistent.cabal
+++ b/elm-export-persistent.cabal
@@ -2,7 +2,7 @@
 -- further documentation, see http://haskell.org/cabal/users-guide/
 
 name:                elm-export-persistent
-version:             0.1.2
+version:             0.2.0
 synopsis:            elm-export persistent entities
 description:
   Ent is a newtype that wraps Persistent Entity's, allowing you to export them
@@ -18,11 +18,9 @@
 build-type:          Simple
 extra-source-files:  ChangeLog.md
 cabal-version:       >=1.10
-tested-with:         GHC == 7.10.1
-                   , GHC == 7.10.2
-                   , GHC == 7.10.3
-                   , GHC == 8.0.1
+tested-with:         GHC == 7.10.3
                    , GHC == 8.0.2
+                   , GHC == 8.2.2
 
 source-repository head
   type:     git
diff --git a/src/Elm/Export/Persist/Ent.hs b/src/Elm/Export/Persist/Ent.hs
--- a/src/Elm/Export/Persist/Ent.hs
+++ b/src/Elm/Export/Persist/Ent.hs
@@ -73,7 +73,7 @@
       keyname :: String
       keyname = symbolVal (Proxy :: Proxy field)
 
-instance (KnownSymbol field, ToJSON a) => ToJSON (Ent field a) where
+instance (KnownSymbol field, ToJSON a, ToJSON (Key a)) => ToJSON (Ent field a) where
   toJSON (Ent (Entity k val)) =
     case toJSON val of
       Object hmap -> Object (Map.insert keyname (toJSON k) hmap)